This invention relates to a ring binder mechanism for retaining loose-leaf pages, and in particular to an improved mechanism for controlling opening and closing movement of rings, for reducing snapping force of closing rings, and for securely holding closed rings in a locked position.
A ring binder mechanism retains loose-leaf pages, such as hole-punched pages, in a file or notebook. It has rings formed by two ring members for retaining the pages. The rings may be selectively opened to add or remove pages to the rings or closed to retain pages on the rings while allowing the pages to move along the rings. The ring members of each ring mount on two adjacent hinge plates. The hinge plates join together about a pivot axis for pivoting movement within an elongate housing. The housing holds the hinge plates so they may pivot relative to the housing and move the ring members between an open position and a closed position.
The undeformed housing is narrower than the joined hinge plates when the hinge plates are in a coplanar position (180°). So as the hinge plates pivot through this position, they deform the resilient housing and cause a spring force in the housing that urges the hinge plates to pivot away from the coplanar position and move the ring members to either their open or closed position. This force is generally large to hold the hinge plates against unwanted separation or opening of the rings. As a result, when the hinge plates move through the co-planar position, they do so with a strong snapping movement. This snaps the ring members together when they close and snaps them apart when they open. When the ring members close, there is a concern that they may rapidly snap together with a force that might cause fingers to be pinched in the ring members.
The housing spring force can also make it difficult to move the hinge plates through the co-planar position. As a result, it may be hard for an operator to open or close the ring members. In addition, the housing may begin to permanently deform over time because of the repeated deformation when pivoting the hinge plates. This may reduce the housing's ability to uniformly hold the ring members together when they are closed and may allow gaps to form between the closed ring members. Pages may escape from the closed rings. Furthermore, in may of these mechanisms the ring members do not positively lock together when they are closed. So if the mechanism is accidentally dropped, the ring members may unintentionally open and allow pages to fall out.
Accordingly, there is a need for a ring binder mechanism in which rings are easy to open and close, in which the ring members of the rings do not strongly snap together, and in which the ring members lock together to securely retain pages on the closed rings.